An innocent selfie prank led to a man’s arrest after friends found disturbing photos on his phone.

18-year-old Kirsty-Ann Barr of the United Kingdom, called police after playing a prank on a man who was living with her and her boyfriend.

Barr said that she became good friends with 24-year-old Nathan Kozel, while he was living with her and her boyfriend in Yorkshire.

She said that after a night of drinking, she and her boyfriend decided to take some selfies on Kozel's phone while he was sitting in their room.

When the couple opened his phone, they found very disturbing photos of children being sexually abused and of a person performing a sex act with a horse.

They immediately called police, who confiscated all of Kozel’s electronic devices, and he was arrested.

He pleaded guilty at the Hull Magistrates' Court to making an indecent image of a child, possession of indecent photographs of children, possessing prohibited images of children and possessing an extreme photographic image of a person performing a sex act with a horse.

Kozel was sentenced to complete 30 days of rehabilitation, he was made subject to a sexual harm prevention order and he was ordered to pay £80 ($103).

Barr said that she was shocked by the lenient sentence her former friend received. “I don't think it’s fair for what he had on his phone,” she said.